App can't connect to server on mobile connection

[TheZoker]

Summary

When I try to connect to my mattermost instance on a mobile connection via the app, the app tells me, that the connection failed. When I'm on wifi, it works. When I'm on a mobile connection and open my instance within a browser, it works. Only mobile connection and app does not work.

I also checked this guide: https://docs.mattermost.com/deploy/mobile-troubleshoot.html#i-keep-getting-a-message-cannot-connect-to-the-server-please-check-your-server-url-and-internet-connection

But my SSL certificate is fine (provided by Let's Encrypt). For my setup I use a reverse proxy (traefik).

Environment Information

• Device Name: Samsung Galaxy S23+
• OS Version: Android 14
• Mattermost App Version: 2.10.1
• Mattermost Server Version: 9.2.3

Steps to reproduce

1. Download app
2. Use mobile connection
3. Connect to server

Expected behavior

Work on mobile connection

Observed behavior (that appears unintentional)

Error is: Cannot connect to the server

Possible fixes

?

[enahum]

Havr you checked your server IPv6 support? It may be related

[TheZoker]

Thanks for the hint! Is there any good way to test this?

If this is the issue, why is there no IPv4 fallback in the app then?

[enahum]

We have this help wanted ticket open https://github.com/mattermost/mattermost/issues/24703

[amyblais]

Closing as a "duplicate" of the Help Wanted issue linked above,